A roughing filter was used to clean very dirty water before passing it through a slow sand filter. The roughing filter successfully reduced the water's cloudiness from 1,000 to 10 NTU. By adjusting the filter media, height, filtration rate, and adding coagulant, the researchers created guidelines for designing effective water treatment plants. These plants in Myanmar produced clean water meeting WHO standards, even with only a year of operation. Regular sand scraping helped maintain the filtration rate.